[ https://issues.apache.org/jira/browse/CASSANDRA-4734?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sylvain Lebresne updated CASSANDRA-4734:
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Attachment: (was: 0002-Remove-remains-of-4448.txt)
> Move CQL3 consistency to protocol
> ---------------------------------
>
> Key: CASSANDRA-4734
> URL: https://issues.apache.org/jira/browse/CASSANDRA-4734
> Project: Cassandra
> Issue Type: Task
> Components: API
> Reporter: Jonathan Ellis
> Assignee: Sylvain Lebresne
> Fix For: 1.2.0 beta 2
>
> Attachments: 0001-Move-consistency-level-to-the-protocol-level.txt, 0002-Remove-remains-of-4448.txt,
0003-Thrift-generated-file-diffs.txt
>
>
> Currently, in CQL3, you set the consistency level of an operation in
> the language, eg 'SELECT * FROM foo USING CONSISTENCY QUORUM'. It now
> looks like this was a mistake, and that consistency should be set at
> the protocol level, i.e. as a separate parameter along with the query.
> The reasoning is that the CL applies to the guarantee provided by the
> operation being successful, not to the query itself. Specifically,
> having the CL being part of the language means that CL is opaque to
> low level client libraries without themselves parsing the CQL, which
> we want to avoid. Thus,
> - Those libraries can't implement automatic retries policy, where a query would be retried
with a smaller CL. (I'm aware that this is often a Bad Idea, but it does have legitimate
uses and not having that available is seen as a regression from the Thrift api.)
> - We had to introduce CASSANDRA-4448 to allow the client to configure some form of default
CL since the library can't handle that anymore, which is hackish.
> - Executing prepared statements with different CL requires preparing multiple statements.
> - CL only makes sense for BATCH operations as a whole, not the sub-statements within
the batch. Currently CQL3 "fixes" that by validating the given CLs match, but it would be
much more clear if the CL was on the protocol side.
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